Consumption of bottled, pasteurized milk processed by a single dairy was associated with an outbreak of Yersinia enterocolitica O:8 infections. No deficiencies in pasteurization procedures or equipment were detected. Yersinia enterocolitica O:8 was isolated in a raw milk sample collected at the dairy and in a fecal sample collected from a dairy pig. This outbreak likely resulted from post-pasteurization contamination of milk. Dairy pigs were the most likely source of contamination. Milk bottles were likely contaminated by rinsing with untreated well water prior to filling or by other environmental routes.